The present invention relates to digital data processing and more particularly to a method and apparatus for buffering data prior to recording in block format on a record medium.
Recording of digital data on a record medium such as magnetic tape or punched paper in association with data communication printers is well known. The recording of data in block format allows for editing of the data prior to recording. It also allows higher density recording of data on the medium as opposed to incremental character recording. Where a recorder has to accommodate data available at different incoming data rates, use has been made of buffering stages of one character length, one block length or an integral number of block lengths. One common approach is to employ a single buffer of one block length. The major disadvantage of this approach is that the data source must wait for the recorder to record the block of data before entry of further data. Another common approach is to use two buffers, each of one block length, wherein as one stored block is being used to drive the recorder, data is being entered into the second buffer. Such an arrangement has proved to be relatively expensive because of its relatively inefficient utilization of electronic circuitry. The latter arrangement has also been unsuitable in applications where space is a premium since two full blocks of buffering is employed. Also some form of switching is generally required to couple the source and recorder sequentially to the two buffers.
Accordingly, it is one object of this invention to provide a data processing arrangement which is more economical and requires less physical space than prior art arrangements.
A further object of this invention is to provide an improved buffering system for buffering the digital data output available from sources at varying rates for application to a recorder operating at a substantially higher rate.
A further object of this invention is to reduce the cost and size of associated auxiliary control functions required in recording data at a high speed from data sources which deliver the data at different rates of speed.
Another object of this invention is to provide an improved digital data processing arrangement.
Another object of this invention is to provide improved circuitry for controlling the operation of a recorder in accordance with the status of digital data being circulated in a recirculating storage register coupled to data sources.
Another object of this invention is to provide an improved control arrangement for detecting the status of data being incremented in a storage register in order to coordinate the transfer of data from the data source to the register, and from the register to the recorder.